Baryon-antibaryon photoproduction cross sections off the proton

The GlueX experiment at Jefferson Lab has observed pp and, for the first time, AA and pA photoproduction from a proton target at photon energies up to 11.6 GeV. The angular distributions are forward peaked for all produced pairs, consistent with Regge-like techannel exchange. Asymmetric wide-angle antibaryon distributions show the presence of additional processes. In a phenomenological model, we find consistency with a doublet-channel exchange process where antibaryons are created only at the middle vertex. The model matches all observed distributions with a small number of free parameters. In the hyperon channels, we observe a clear distinction between photoproduction of the AA and pA systems but general similarity to the pp system. We report both total cross sections and cross sections differential with respect to momentum transfer and the invariant masses of the created particle pairs. No narrow resonant structures were found in these reaction channels. The suppression of ss quark pairs relative to dd quark pairs is similar to what has been seen in other reactions.

Duke Scholars

Author Haiyan Gao Physics